What Causes Pain And Swelling In Neck?

Hello I am a 46yr old male that has had a pian in the right side of my neck for over three weeks. I have not been able to sleep ir I have been very resless. For the most part it feels like just a sore or stiff pain. If I tilt my head to the right as if I were going to touch my ear to my shoulder there feels to be some swelling. Really lost on this one...... Sam